Are the demon-possessed responsible for being in that condition?

Were those of whom we read in the New Testament that they were demon-possessed responsible for being in that condition?

Certainly not in every case. In that of the boy in Mark 9:20-22, his father in reply to the Lord’s question said that he had been thus from childhood. What was true with regard to the other miracles of healing wrought by Christ was probably true of the demon-possessed also, that in some instances the trouble was due to sin on the part of the person concerned, and in others not so. Contrast the warning to the impotent man in John 5:14, “Sin no more, lest a worse thing come unto thee,” with the words spoken of the blind man in John 9.3, “Neither hath this man sinned.”

W.R.